Subsurface seismic exploration is presently based on elastic wave test signals remotely detected by sensors (geophones) and evaluated using well known geophysical methods. Said test signals can be the result of surface of subsurface natural or artificial signal source (the source) generating elastic waves (seismic waves), where seismic waves travel through underground media and, by way of substantially unchanged wave travel or by way of reflection, refraction and other forms of wave changing travel, reach a receiving sensor array. A receiving sensor array comprises multiple seismic sensors regularly arranged and carefully located to optimally detect original or changed seismic waves and to transduce sensed elastic waves into electrical signals for input by electrical connection with a signal acquisition system recording said transduced data through signal processing and analysis, to determine the geometry and physical characteristics of the subsurface.
Traditional seismic data acquisition is made by the well-known artificial plug detector method, whose efficiency is limited because of a requirement for multiple fixed placements and removals of sensors in an array. Quick deployment and use of a land geophone receiver array for the seismic exploration has been the subject of intense investigation and experimentation. Over the last decade, the United States National Science Foundation (NSF), Department of Energy (DOE), and the Department of Defense (DOD) have invested substantial amounts toward these and related subjects. PFM Manufacturing Company (Montana Tech and PFM Manufacturing) have developed under the U.S. National Science Foundation a set of marine seismic exploration buoys, a land-use zones sensor array (land streamer), and a four-sensor array with for land using multiple, parallel sets of said arrays.
It is known to use a vehicle to pull behind it an array of seismic sensors over the surface of the ground. However, there are severe limitations to the use of such systems. Each seismic sensor must be directed downward and, in use, be generally aligned normal to the curvature of the Earth at the point of contact. It is an inherent requirement of seismic sensors that they not only be in contact with the Earth but are preferably inserted into it to improve seismic wave detection. The pull-behind seismic sensor array systems are inherently barred from using seismic sensors which are insertable into the surface. The underside of each such geophone must be sufficiently smooth so that it can be easily dragged forward by a vehicle without deflection. Even a small amount of deflection of a detecting geophone causes collected data to be essentially worthless. Thus, such pull-behind systems are of little value unless the entire intended path of the pulled array is smoothed almost to the point of forming a road surface. A desired set of surfaces for application of an array of geophones may be located in an area where such smoothing is impractical or not economical or where insertable geophone housings may be required for effective wave detection. There is a need for a geophone array system which overcomes the limitations of the pull-behind systems while preserving their advantages.
The surfaces upon which the pull-behind system can be practiced are very limited. University of Kansas and the United States for nearly 10 years studied small 3D-array detector devices. U.S. Pat. No. 6,532,190 for a seismic sensor array discloses multiple sensors implanted by way of hydraulic implantation in a detector array, but the seismic sensors each must be fixed in a rigid housing and driven into the ground requiring flat, rigid steel housings introducing wave interference which negatively affect measurement accuracy. In addition, Switzerland, ETH, Denmark COWI, Kansas Geological Survey, Ramboll Sweden and other companies have developed pull-behind systems based on towing sets of parallel cables to which seismic sensors have been fixed to an underside.